10 Gallon CRS Minimalist
That's really neat!!
To be honest, I wouldn't invest in one just yet.
It is really easy to buy 1gallon jugs of RO water (green Cap at Walmart) at .88¢ each or RO refills from the Walmart culligan machine for .37¢ each gallon.
RO units pay off over time, and for one or two nanos, I might just suggest doing the jug method.
To keep a good CRS tank, you'll be doing minimal water changes, just top offs and bi-weekly changes if you don't keep floaters. So you won't need much water.